1. Field
This disclosure relates generally to techniques for performing wellsite operations. More specifically, the disclosure relates to techniques, such as drilling motors (and related valves) used in drilling wellbores.
2. Description of Related Art
In the oil and gas exploration and production industry, subsurface formations are accessed by drilling boreholes from the surface. Typically, a drill bit is mounted on the lower end of a tubular string of pipe (referred to as a “drill string”), and advanced into the earth from the surface to form a wellbore. A drilling motor is positioned along the drill string to perform various functions, such as providing power to the drill bit to drill the wellbore. Drilling fluid or “mud” may be pumped down through the drill string from the surface and exited through nozzles in the drill bit. The drilling fluid may carry drill cuttings out of the borehole, and back up to the surface through an annulus between the drill pipe and the wellbore wall. As the fluid passes through the drilling mud motor, a rotor positioned in a stator of the drilling motor may be driven.
A conventional drilling mud motor may be, for example, a progressive cavity or Moineau motor having helical fixed stator with a rotational rotor positioned therein. Typically, the rotor has multiple spiral lobes for engaging a greater number of spiral grooves formed in the rubber stator. Drilling mud (or other suitable fluid) may be pumped into the space between the rotor and the stator. The drilling mud may be pumped through the motor and forced along a progressive cavity therein, thereby causing the rotor to rotate in an eccentric manner. Other drilling motors, such as turbine driven motors with turbine rotors have also been developed.
In some cases, it may be desirable to control the flow of fluid as it passes through the drill string as described, for example, in U.S. Pat. Nos. 7,086,486, 4,979,577, and 4,275,795. The fluid flow may be used in an attempt to provide a percussive or hammer effect as described in U.S. Pat. No. 6,508,317, which hereby is incorporated by reference herein.
Despite the development of techniques for controlling fluid flow through a drill string, there remains a need to provide advanced techniques for controlling flow. It may be desirable to provide techniques that may be used to assist in preventing the drilling tool from sticking in the wellbore. It may be further desirable that such techniques reduce vibration and/or increase drilling efficiency in the downhole tool, while preventing damage to the bit. This disclosure is directed to fulfilling this need in the art.